Earthworm Watch: Insights into urban earthworm communities in the UK using citizen science

The distribution of earthworm ecological groups in urban areas is not well-known, despite their crucial role in delivering soil ecosystem services such as nutrient cycling and water drainage. Citizen science engages public audiences in the scientific research process and is an excellent tool for collecting biodiversity data in urban areas, where most of the UK population resides. However, a disadvantage is that differing levels of skill and engagement among participants can create statistical challenges. The Earthworm Watch citizen science project used 668 matched-pair surveys to estimate how the abundance and ecological diversity of earthworms respond to land management practices, and soil properties in UK urban habitats. A total of 5170 earthworms were counted during the project with a mean of 8 earthworms per soil pit - equivalent to a density of 198 earthworms per m². Soil moisture and texture were the largest drivers of total earthworm abundance, with habitat borderline statistically insignificant. Endogeic earthworms were found in 71 % of soil pits, epigeic in 62 % and anecic in 33 %. Fertiliser use also had a significant effect on total abundance, but only when organic fertiliser was used. Earthworm ecological groups demonstrated varied responses to habitat, with endogeic earthworms consistently the most abundant group, showing slight preferences for grasslands and vegetable beds. Anecic earthworms had the lowest abundance across all habitats but were more prevalent in grasslands and vegetable beds. Epigeic earthworms were most abundant beneath shrubs and hedges. These findings align with expected patterns of earthworm ecology, underscoring the potential of well-designed citizen science projects to yield valuable insights into urban earthworms and soil health.